diff --git a/addon-sdk/source/lib/sdk/addon/installer.js b/addon-sdk/source/lib/sdk/addon/installer.js
index f72b21e0a28..451ad224c0a 100644
--- a/addon-sdk/source/lib/sdk/addon/installer.js
+++ b/addon-sdk/source/lib/sdk/addon/installer.js
@@ -87,20 +87,24 @@ exports.uninstall = function uninstall(addonId) {
   AddonManager.addAddonListener(listener);
 
   // Order Addonmanager to uninstall the addon
-  AddonManager.getAddonByID(addonId, function (addon) {
-    addon.uninstall();
-  });
+  getAddon(addonId).then(addon => addon.uninstall(), reject);
 
   return promise;
 };
 
 exports.disable = function disable(addonId) {
-  let { promise, resolve, reject } = defer();
-
-  AddonManager.getAddonByID(addonId, function (addon) {
+  return getAddon(addonId).then(addon => {
     addon.userDisabled = true;
-    resolve();
+    return addonId;
   });
-
-  return promise;
 };
+
+exports.isActive = function isActive(addonId) {
+  return getAddon(addonId).then(addon => addon.isActive && !addon.appDisabled);
+};
+
+function getAddon (id) {
+  let { promise, resolve, reject } = defer();
+  AddonManager.getAddonByID(id, addon => addon ? resolve(addon) : reject());
+  return promise;
+}
diff --git a/addon-sdk/source/lib/sdk/content/worker.js b/addon-sdk/source/lib/sdk/content/worker.js
index 4d8bceca9fc..d781f39c239 100644
--- a/addon-sdk/source/lib/sdk/content/worker.js
+++ b/addon-sdk/source/lib/sdk/content/worker.js
@@ -130,13 +130,13 @@ const WorkerSandbox = EventEmitter.compose({
     // Even if this principal is for a domain that is specified in the multiple
     // domain principal.
     let principals  = window;
-    let wantXHRConstructor = false;
+    let wantDOMConstructors = []
     if (EXPANDED_PRINCIPALS.length > 0 && !worker._injectInDocument) {
       principals = EXPANDED_PRINCIPALS.concat(window);
       // We have to replace XHR constructor of the content document
       // with a custom cross origin one, automagically added by platform code:
       delete proto.XMLHttpRequest;
-      wantXHRConstructor = true;
+      wantDOMConstructors.push("XMLHttpRequest");
     }
 
     // Instantiate trusted code in another Sandbox in order to prevent content
@@ -149,7 +149,7 @@ const WorkerSandbox = EventEmitter.compose({
     let content = this._sandbox = sandbox(principals, {
       sandboxPrototype: proto,
       wantXrays: true,
-      wantXHRConstructor: wantXHRConstructor,
+      wantDOMConstructors: wantDOMConstructors,
       sameZoneAs: window
     });
     // We have to ensure that window.top and window.parent are the exact same
diff --git a/addon-sdk/source/lib/sdk/hotkeys.js b/addon-sdk/source/lib/sdk/hotkeys.js
index ce47191b225..00081455e6a 100644
--- a/addon-sdk/source/lib/sdk/hotkeys.js
+++ b/addon-sdk/source/lib/sdk/hotkeys.js
@@ -24,7 +24,7 @@ const Hotkey = exports.Hotkey = function Hotkey(options) {
     throw new TypeError(INVALID_HOTKEY);
   }
 
-  this.onPress = options.onPress;
+  this.onPress = options.onPress && options.onPress.bind(this);
   this.toString = stringify.bind(null, hotkey);
   // Registering listener on keyboard combination enclosed by this hotkey.
   // Please note that `this.toString()` is a normalized version of
diff --git a/addon-sdk/source/lib/sdk/util/deprecate.js b/addon-sdk/source/lib/sdk/util/deprecate.js
index be3ca64508a..40f236de524 100644
--- a/addon-sdk/source/lib/sdk/util/deprecate.js
+++ b/addon-sdk/source/lib/sdk/util/deprecate.js
@@ -9,12 +9,16 @@ module.metadata = {
 };
 
 const { get, format } = require("../console/traceback");
+const { get: getPref } = require("../preferences/service");
+const PREFERENCE = "devtools.errorconsole.deprecation_warnings";
 
 function deprecateUsage(msg) {
   // Print caller stacktrace in order to help figuring out which code
   // does use deprecated thing
   let stack = get().slice(2);
-  console.error("DEPRECATED: " + msg + "\n" + format(stack));
+
+  if (getPref(PREFERENCE)) 
+    console.error("DEPRECATED: " + msg + "\n" + format(stack));
 }
 exports.deprecateUsage = deprecateUsage;
 
diff --git a/addon-sdk/source/test/private-browsing/global.js b/addon-sdk/source/test/private-browsing/global.js
index 22ac59e67e9..199a853a2f3 100644
--- a/addon-sdk/source/test/private-browsing/global.js
+++ b/addon-sdk/source/test/private-browsing/global.js
@@ -7,6 +7,8 @@ const timer = require("sdk/timers");
 const { LoaderWithHookedConsole, deactivate, pb, pbUtils } = require("./helper");
 const tabs = require("sdk/tabs");
 const { getMostRecentBrowserWindow, isWindowPrivate } = require('sdk/window/utils');
+const { set: setPref } = require("sdk/preferences/service");
+const DEPRECATE_PREF = "devtools.errorconsole.deprecation_warnings";
 
 exports["test activate private mode via handler"] = function(test) {
   test.waitUntilDone();
@@ -174,6 +176,7 @@ exports.testBothListeners = function(test) {
 
 exports.testAutomaticUnload = function(test) {
   test.waitUntilDone();
+  setPref(DEPRECATE_PREF, true);
 
   // Create another private browsing instance and unload it
   let { loader, errors } = LoaderWithHookedConsole(module);
diff --git a/addon-sdk/source/test/tabs/test-fennec-tabs.js b/addon-sdk/source/test/tabs/test-fennec-tabs.js
index b841589e89a..e579ebba93d 100644
--- a/addon-sdk/source/test/tabs/test-fennec-tabs.js
+++ b/addon-sdk/source/test/tabs/test-fennec-tabs.js
@@ -8,6 +8,8 @@ const { Loader, LoaderWithHookedConsole } = require('sdk/test/loader');
 const timer = require('sdk/timers');
 const tabs = require('sdk/tabs');
 const windows = require('sdk/windows');
+const { set: setPref } = require("sdk/preferences/service");
+const DEPRECATE_PREF = "devtools.errorconsole.deprecation_warnings";
 
 const tabsLen = tabs.length;
 const URL = 'data:text/html;charset=utf-8,<html><head><title>#title#</title></head></html>';
@@ -96,6 +98,7 @@ exports.testAutomaticDestroy = function(assert, done) {
 
 // TEST: tab properties
 exports.testTabProperties = function(assert, done) {
+  setPref(DEPRECATE_PREF, true);
   let { loader, messages } = LoaderWithHookedConsole();
   let tabs = loader.require('sdk/tabs');
 
diff --git a/addon-sdk/source/test/tabs/test-firefox-tabs.js b/addon-sdk/source/test/tabs/test-firefox-tabs.js
index 8777fd9e071..d3c5294ed2c 100644
--- a/addon-sdk/source/test/tabs/test-firefox-tabs.js
+++ b/addon-sdk/source/test/tabs/test-firefox-tabs.js
@@ -12,6 +12,8 @@ const { open, focus, close } = require('sdk/window/helpers');
 const { StringBundle } = require('sdk/deprecated/app-strings');
 const tabs = require('sdk/tabs');
 const { browserWindows } = require('sdk/windows');
+const { set: setPref } = require("sdk/preferences/service");
+const DEPRECATE_PREF = "devtools.errorconsole.deprecation_warnings";
 
 const base64png = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQImWNgYGBgAA";
 
@@ -904,6 +906,7 @@ exports.testOnLoadEventWithImage = function(assert, done) {
 };
 
 exports.testFaviconGetterDeprecation = function (assert, done) {
+  setPref(DEPRECATE_PREF, true);
   const { LoaderWithHookedConsole } = require("sdk/test/loader");
   let { loader, messages } = LoaderWithHookedConsole(module);
   let tabs = loader.require('sdk/tabs');
diff --git a/addon-sdk/source/test/test-addon-installer.js b/addon-sdk/source/test/test-addon-installer.js
index a816799ac51..0938c23bba0 100644
--- a/addon-sdk/source/test/test-addon-installer.js
+++ b/addon-sdk/source/test/test-addon-installer.js
@@ -48,7 +48,7 @@ exports["test Install"] = function (assert, done) {
       done();
     }
   );
-}
+};
 
 exports["test Failing Install With Invalid Path"] = function (assert, done) {
   AddonInstaller.install("invalid-path").then(
@@ -62,7 +62,7 @@ exports["test Failing Install With Invalid Path"] = function (assert, done) {
       done();
     }
   );
-}
+};
 
 exports["test Failing Install With Invalid File"] = function (assert, done) {
   let directory = system.pathFor("ProfD");
@@ -131,6 +131,38 @@ exports["test Update"] = function (assert, done) {
   }
 
   next();
-}
+};
+
+exports['test Uninstall failure'] = function (assert, done) {
+  AddonInstaller.uninstall('invalid-addon-path').then(
+    () => assert.fail('Addon uninstall should not resolve successfully'),
+    () => assert.pass('Addon correctly rejected invalid uninstall')
+  ).then(done, assert.fail);
+};
+
+exports['test Addon Disable'] = function (assert, done) {
+  let ensureActive = (addonId) => AddonInstaller.isActive(addonId).then(state => {
+    assert.equal(state, true, 'Addon should be enabled by default');
+    return addonId;
+  });
+  let ensureInactive = (addonId) => AddonInstaller.isActive(addonId).then(state => {
+    assert.equal(state, false, 'Addon should be disabled after disabling');
+    return addonId;
+  });
+
+  AddonInstaller.install(ADDON_PATH)
+    .then(ensureActive)
+    .then(AddonInstaller.disable)
+    .then(ensureInactive)
+    .then(AddonInstaller.uninstall)
+    .then(done, assert.fail);
+};
+
+exports['test Disable failure'] = function (assert, done) {
+  AddonInstaller.disable('not-an-id').then(
+    () => assert.fail('Addon disable should not resolve successfully'),
+    () => assert.pass('Addon correctly rejected invalid disable')
+  ).then(done, assert.fail);
+};
 
 require("test").run(exports);
diff --git a/addon-sdk/source/test/test-addon-page.js b/addon-sdk/source/test/test-addon-page.js
index 7cc6a4edaf0..fc885e377a0 100644
--- a/addon-sdk/source/test/test-addon-page.js
+++ b/addon-sdk/source/test/test-addon-page.js
@@ -18,6 +18,8 @@ const { setTimeout } = require('sdk/timers');
 const { is } = require('sdk/system/xul-app');
 const tabs = require('sdk/tabs');
 const isAustralis = "gCustomizeMode" in windows.activeBrowserWindow;
+const { set: setPref } = require("sdk/preferences/service");
+const DEPRECATE_PREF = "devtools.errorconsole.deprecation_warnings";
 
 let uri = require('sdk/self').data.url('index.html');
 
@@ -29,6 +31,7 @@ function isChromeVisible(window) {
 exports['test add-on page deprecation message'] = function(assert) {
   let { loader, messages } = LoaderWithHookedConsole(module);
   loader.require('sdk/addon-page');
+  setPref(DEPRECATE_PREF, true);
 
   assert.equal(messages.length, 1, "only one error is dispatched");
   assert.equal(messages[0].type, "error", "the console message is an error");
diff --git a/addon-sdk/source/test/test-content-events.js b/addon-sdk/source/test/test-content-events.js
index f4a7b164479..9ec694f2530 100644
--- a/addon-sdk/source/test/test-content-events.js
+++ b/addon-sdk/source/test/test-content-events.js
@@ -41,7 +41,9 @@ exports["test multiple tabs"] = function(assert, done) {
   let { events } = loader.require("sdk/content/events");
   let { on, off } = loader.require("sdk/event/core");
   let actual = [];
-  on(events, "data", function({type, target, timeStamp}) {
+
+  on(events, "data", handler);
+  function handler ({type, target, timeStamp}) {
     // ignore about:blank pages and *-document-global-created
     // events that are not very consistent.
     // ignore http:// requests, as Fennec's `about:home` page
@@ -52,7 +54,7 @@ exports["test multiple tabs"] = function(assert, done) {
         type !== "chrome-document-global-created" &&
         type !== "content-document-global-created")
       actual.push(type + " -> " + target.URL)
-  });
+  }
 
   let window = getMostRecentBrowserWindow();
   let firstTab = open("data:text/html,first-tab", window);
@@ -78,6 +80,7 @@ exports["test multiple tabs"] = function(assert, done) {
       assert.fail(Error(reason));
     }).then(function() {
       loader.unload();
+      off(events, "data", handler);
       done();
     });
 };
@@ -87,14 +90,15 @@ exports["test nested frames"] = function(assert, done) {
   let { events } = loader.require("sdk/content/events");
   let { on, off } = loader.require("sdk/event/core");
   let actual = [];
-  on(events, "data", function({type, target, timeStamp}) {
+  on(events, "data", handler);
+  function handler ({type, target, timeStamp}) {
     // ignore about:blank pages and *-global-created
     // events that are not very consistent.
     if (target.URL !== "about:blank" &&
        type !== "chrome-document-global-created" &&
        type !== "content-document-global-created")
       actual.push(type + " -> " + target.URL)
-  });
+  }
 
   let window =  getMostRecentBrowserWindow();
   let uri = encodeURI("data:text/html,<iframe src='data:text/html,iframe'>");
@@ -117,6 +121,7 @@ exports["test nested frames"] = function(assert, done) {
       assert.fail(Error(reason))
     }).then(function() {
       loader.unload();
+      off(events, "data", handler);
       done();
     });
 };
diff --git a/addon-sdk/source/test/test-content-worker.js b/addon-sdk/source/test/test-content-worker.js
index e33b9a5e273..2fa8d9621f9 100644
--- a/addon-sdk/source/test/test-content-worker.js
+++ b/addon-sdk/source/test/test-content-worker.js
@@ -16,6 +16,8 @@ const { setTimeout } = require("sdk/timers");
 const { LoaderWithHookedConsole } = require("sdk/test/loader");
 const { Worker } = require("sdk/content/worker");
 const { close } = require("sdk/window/helpers");
+const { set: setPref } = require("sdk/preferences/service");
+const DEPRECATE_PREF = "devtools.errorconsole.deprecation_warnings";
 
 const DEFAULT_CONTENT_URL = "data:text/html;charset=utf-8,foo";
 
@@ -658,6 +660,7 @@ exports["test:global postMessage"] = WorkerTest(
   DEFAULT_CONTENT_URL,
   function(assert, browser, done) {
     let { loader } = LoaderWithHookedConsole(module, onMessage);
+    setPref(DEPRECATE_PREF, true);
 
     // Intercept all console method calls
     let seenMessages = 0;
diff --git a/addon-sdk/source/test/test-deprecate.js b/addon-sdk/source/test/test-deprecate.js
index b3afc1e750c..ce306b15b78 100644
--- a/addon-sdk/source/test/test-deprecate.js
+++ b/addon-sdk/source/test/test-deprecate.js
@@ -2,10 +2,15 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+'use strict';
+
 const deprecate = require("sdk/util/deprecate");
 const { LoaderWithHookedConsole } = require("sdk/test/loader");
+const { get, set } = require("sdk/preferences/service");
+const PREFERENCE = "devtools.errorconsole.deprecation_warnings";
 
 exports["test Deprecate Usage"] = function testDeprecateUsage(assert) {
+  set(PREFERENCE, true);
   let { loader, messages } = LoaderWithHookedConsole(module);
   let deprecate = loader.require("sdk/util/deprecate");
 
@@ -31,6 +36,7 @@ exports["test Deprecate Usage"] = function testDeprecateUsage(assert) {
 }
 
 exports["test Deprecate Function"] = function testDeprecateFunction(assert) {
+  set(PREFERENCE, true);
   let { loader, messages } = LoaderWithHookedConsole(module);
   let deprecate = loader.require("sdk/util/deprecate");
 
@@ -63,6 +69,7 @@ exports["test Deprecate Function"] = function testDeprecateFunction(assert) {
 }
 
 exports.testDeprecateEvent = function(assert, done) {
+  set(PREFERENCE, true);
   let { loader, messages } = LoaderWithHookedConsole(module);
   let deprecate = loader.require("sdk/util/deprecate");
 
@@ -91,4 +98,63 @@ exports.testDeprecateEvent = function(assert, done) {
   emit(testObj, 'fire');
 }
 
+exports.testDeprecateSettingToggle = function (assert, done) {
+  let { loader, messages } = LoaderWithHookedConsole(module);
+  let deprecate = loader.require("sdk/util/deprecate");
+  
+  function fn () { deprecate.deprecateUsage("foo"); }
+
+  set(PREFERENCE, false);
+  fn();
+  assert.equal(messages.length, 0, 'no deprecation warnings');
+  
+  set(PREFERENCE, true);
+  fn();
+  assert.equal(messages.length, 1, 'deprecation warnings when toggled');
+
+  set(PREFERENCE, false);
+  fn();
+  assert.equal(messages.length, 1, 'no new deprecation warnings');
+  done();
+};
+
+exports.testDeprecateSetting = function (assert, done) {
+  // Set devtools.errorconsole.deprecation_warnings to false
+  set(PREFERENCE, false);
+
+  let { loader, messages } = LoaderWithHookedConsole(module);
+  let deprecate = loader.require("sdk/util/deprecate");
+
+  // deprecateUsage test
+  function functionIsDeprecated() {
+    deprecate.deprecateUsage("foo");
+  }
+  functionIsDeprecated();
+
+  assert.equal(messages.length, 0,
+    "no errors dispatched on deprecateUsage");
+
+  // deprecateFunction test
+  function originalFunction() {};
+
+  let deprecateFunction = deprecate.deprecateFunction(originalFunction,
+                                                       "bar");
+  deprecateFunction();
+
+  assert.equal(messages.length, 0,
+    "no errors dispatched on deprecateFunction");
+
+  // deprecateEvent
+  let { on, emit } = loader.require('sdk/event/core');
+  let testObj = {};
+  testObj.on = deprecate.deprecateEvent(on.bind(null, testObj), 'BAD', ['fire']);
+
+  testObj.on('fire', () => {
+    assert.equal(messages.length, 0,
+      "no errors dispatched on deprecateEvent");
+    done();
+  });
+
+  emit(testObj, 'fire');
+}
 require("test").run(exports);
diff --git a/addon-sdk/source/test/test-hotkeys.js b/addon-sdk/source/test/test-hotkeys.js
index 7dc590f8872..77fe9a45de0 100644
--- a/addon-sdk/source/test/test-hotkeys.js
+++ b/addon-sdk/source/test/test-hotkeys.js
@@ -16,6 +16,8 @@ exports["test hotkey: function key"] = function(assert, done) {
     combo: "f1",
     onPress: function() {
       assert.pass("first callback is called");
+      assert.equal(this, showHotKey,
+        'Context `this` in `onPress` should be the hotkey object');
       keyDown(element, "f2");
       showHotKey.destroy();
     }
diff --git a/addon-sdk/source/test/test-panel.js b/addon-sdk/source/test/test-panel.js
index 5134764fc62..67f4471e842 100644
--- a/addon-sdk/source/test/test-panel.js
+++ b/addon-sdk/source/test/test-panel.js
@@ -24,6 +24,7 @@ const { pb } = require('./private-browsing/helper');
 const { URL } = require('sdk/url');
 
 const SVG_URL = self.data.url('mofo_logo.SVG');
+const Isolate = fn => '(' + fn + ')()';
 
 function ignorePassingDOMNodeWarning(type, message) {
   if (type !== 'warn' || !message.startsWith('Passing a DOM node'))
@@ -166,54 +167,53 @@ exports["test Document Reload"] = function(assert, done) {
 exports["test Parent Resize Hack"] = function(assert, done) {
   const { Panel } = require('sdk/panel');
 
-  let browserWindow = Cc["@mozilla.org/appshell/window-mediator;1"].
-                      getService(Ci.nsIWindowMediator).
-                      getMostRecentWindow("navigator:browser");
-  let docShell = browserWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                  .getInterface(Ci.nsIWebNavigation)
-                  .QueryInterface(Ci.nsIDocShell);
-  if (!("allowWindowControl" in docShell)) {
-    // bug 635673 is not fixed in this firefox build
-    assert.pass("allowWindowControl attribute that allow to fix browser window " +
-              "resize is not available on this build.");
-    return;
-  }
+  let browserWindow = getMostRecentBrowserWindow();
 
-  let previousWidth = browserWindow.outerWidth, previousHeight = browserWindow.outerHeight;
+  let previousWidth = browserWindow.outerWidth;
+  let previousHeight = browserWindow.outerHeight;
 
   let content = "<script>" +
                 "function contentResize() {" +
                 "  resizeTo(200,200);" +
                 "  resizeBy(200,200);" +
+                "  window.postMessage('resize-attempt', '*');" +
                 "}" +
                 "</script>" +
                 "Try to resize browser window";
+
   let panel = Panel({
     contentURL: "data:text/html;charset=utf-8," + encodeURIComponent(content),
-    contentScript: "self.on('message', function(message){" +
-                   "  if (message=='resize') " +
-                   "    unsafeWindow.contentResize();" +
-                   "});",
     contentScriptWhen: "ready",
-    onMessage: function (message) {
+    contentScript: Isolate(() => {
+        self.on('message', message => {
+          if (message === 'resize') unsafeWindow.contentResize();
+        });
 
+        window.addEventListener('message', ({ data }) => self.postMessage(data));
+      }),
+    onMessage: function (message) {
+      if (message !== "resize-attempt") return;
+
+      assert.equal(browserWindow, getMostRecentBrowserWindow(),
+        "The browser window is still the same");
+      assert.equal(previousWidth, browserWindow.outerWidth,
+        "Size doesn't change by calling resizeTo/By/...");
+      assert.equal(previousHeight, browserWindow.outerHeight,
+        "Size doesn't change by calling resizeTo/By/...");
+
+      try {
+        panel.destroy();
+      }
+      catch (e) {
+        assert.fail(e);
+        throw e;
+      }
+
+      done();
     },
-    onShow: function () {
-      panel.postMessage('resize');
-      timer.setTimeout(function () {
-        assert.equal(previousWidth,browserWindow.outerWidth,"Size doesn't change by calling resizeTo/By/...");
-        assert.equal(previousHeight,browserWindow.outerHeight,"Size doesn't change by calling resizeTo/By/...");
-        try {
-          panel.destroy();
-        }
-        catch (e) {
-          console.exception(e);
-          throw e;
-        }
-        done();
-      },0);
-    }
+    onShow: () => panel.postMessage('resize')
   });
+
   panel.show();
 }
 
diff --git a/addon-sdk/source/test/test-private-browsing.js b/addon-sdk/source/test/test-private-browsing.js
index adeff53b0b1..0242490898a 100644
--- a/addon-sdk/source/test/test-private-browsing.js
+++ b/addon-sdk/source/test/test-private-browsing.js
@@ -18,6 +18,8 @@ const { getMode, isGlobalPBSupported,
         isWindowPBSupported, isTabPBSupported } = require('sdk/private-browsing/utils');
 const { pb } = require('./private-browsing/helper');
 const prefs = require('sdk/preferences/service');
+const { set: setPref } = require("sdk/preferences/service");
+const DEPRECATE_PREF = "devtools.errorconsole.deprecation_warnings";
 
 const kAutoStartPref = "browser.privatebrowsing.autostart";
 
@@ -55,6 +57,7 @@ exports.testIsPrivateDefaults = function(test) {
 };
 
 exports.testWindowDefaults = function(test) {
+  setPref(DEPRECATE_PREF, true);
   // Ensure that browserWindow still works while being deprecated
   let { loader, messages } = LoaderWithHookedConsole(module);
   let windows = loader.require("sdk/windows").browserWindows;
diff --git a/addon-sdk/source/test/test-xhr.js b/addon-sdk/source/test/test-xhr.js
index 257e07964d5..25407be684d 100644
--- a/addon-sdk/source/test/test-xhr.js
+++ b/addon-sdk/source/test/test-xhr.js
@@ -6,11 +6,13 @@
 const { XMLHttpRequest } = require('sdk/net/xhr');
 const { LoaderWithHookedConsole } = require('sdk/test/loader');
 const { data } = require('sdk/self');
-
+const { set: setPref } = require("sdk/preferences/service");
+const DEPRECATE_PREF = "devtools.errorconsole.deprecation_warnings";
 
 exports.testAPIExtension = function(assert) {
   let { loader, messages } = LoaderWithHookedConsole(module);
   let { XMLHttpRequest } = loader.require("sdk/net/xhr");
+  setPref(DEPRECATE_PREF, true);
 
   let xhr = new XMLHttpRequest();
   assert.equal(typeof(xhr.forceAllowThirdPartyCookie), "function",